In recent years, a cutting tool having a longer tool life than conventional ones has been required, along with an increase in demand for more highly efficient cutting. Thus, in terms of the performance required for tool materials, improvements of wear resistance and fracture resistance, which are related to the life of a cutting tool, have been becoming increasingly important. In view of this, in order to improve such characteristics, a coated cutting tool is widely used which includes: a substrate formed of a cemented carbide, cermet, cBN, or the like; and a coating layer provided on the surface of the substrate, the coating layer consisting of one layer or two or more layers each formed of a TiN layer, a TiAlN layer, or the like.
Various techniques have been proposed in order to improve the characteristics of the above-described coating layer. For example, Patent Document 1 proposes a coated cutting tool formed of a composite nitride layer of Al and Ti, in which the lattice constant of the composite nitride layer of Al and Ti takes a value in a range of from −0.057x+4.18 (Å) to −0.057x+4.24 (Å) (x denotes the content of Al and satisfies 0.40≤x≤0.75), and a ratio I (200)/I (111) of a diffraction peak intensity I (200) of a plane (200) to a diffraction peak intensity I (111) of a plane (111) of the composite nitride layer of Al and Ti, which is obtained through X-ray diffraction, is three or more.